CVM Trouble Shooting Guide – Panels only move in increments / Erratic presets
The number one reported issue / problem with the CVM control system is that the presets are erratic. It is also noticed that the panels may only move in increments when in fact they should continually run once the Ctrl 1 or 2 buttons are pressed. When a panel motor only moves in increments, about 2 or 3 inches and then stops, this indicates that the CVM board is not receiving the positioning signal from its respective encoder. Some of Stewart Filmscreen’s older CVM products use special motors with “internal” encoders while present day products are using “external” type motor encoders. These are mounted at the head of the motor.
We have found that most of these types of problems actually can be traced to faulty communication wiring to the CVM board. We have even seen cases whereby the actual CVM’s Ethernet cables were not even plugged into the board. The encoder & motor gears also can be problematic if they are not functioning properly.
We also know that 3rd party control systems can send faulty code to the CVM board causing erratic or lost presets. It is imperative to disconnect the 3rd party control system & only use the supplied 11 button keypad when performing these trouble shooting steps.
- Check both Ethernet cables from each motor to the CVM. Make sure they are plugged in correctly at both ends. Turn off power to the board and re-snap the plugs into the sockets a couple of times. This can correct a faulty connection of the internal pins.
- Make sure these cables have not been crossed. Channel A is the left panel and Channel B is the right channel. Once crossed the panel motors will continue to move incrementally and preset storage is impossible.
- Check for bad crimps. Some customers have made or modified the encoder cables and as a result may have a bad crimp at one of the plugs. Use a cable tester to test the cable and repair the terminations or replace the cable if needed. A new network IP cable may be required.
- Each encoder cable should not exceed 16 feet in length. Do not place the CVM at a greater distance from the product and lengthen the encoder cables. Erratic or faulty control will result when extended encoder cables are used.
- If you are sure that all the cables, plugs and jacks are working correctly then the system should be operating properly & all presets will be permanently saved in the board’s firmware. Once re-connected, the 3rd party control system “duplicates” the functions of the 11 button keypad.
- Replace encoder if necessary. This is extremely rare but like any electronic component the possibility of failure cannot be totally ruled out. We have seen these modules get damaged during the installation phase of the product.
- Check the encoder & motor gears. Make sure both gears are meshing correctly when the motor is moving. If the small gear is out of alignment with the larger gear on the roller tube, the encoder will send faulty code to the board. Re-adjust the encoder mounting if needed. Also check the small set screw on the gear and make sure it is tightened down. If this screw is loose, the encoder will send faulty code. (See photo below).
- Floating keypad issues. We have learned over the years that most customers leave the factory installed keypad "floating" (not installed into a J-Box) behind the screen as they are ultimately using 3rd party networks to control the panels. We ship the keypad with a short pigtail for testing the panels during the installation phase. Ultimately this short keypad cable should be replaced when the keypad is permanently mounted in its final location. When the keypad "floats" in free air or when users are handling it to control the panels, this presents an opportunity for an intermittent on the connector's internal pins. This intermittent connection could also occur when the keypad is placed back onto the floor behind the screen. Should this happen, the 3rd party controller can also misfire as a result. A recommendation would be to unplug the keypad if it is not going to be used or left floating on the floor behind the screen. In that way, the 3rd party control network will function properly.
Photo of an externally mounted encoder
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